A few months ago the little dude started responding to yes/no questions. Around the same time, we began using questions that we knew would elicit a “das” (yes) as a way of distracting him from a grump. “Hey, should we have a banana?”, that sort of thing.
Yesterday I realised that he has learnt to associate that tone of voice with doing something he likes.
I can ask him a question he can’t possibly comprehend in that tone and he will reliably and emphatically say “das”.